1. Technical Field
The invention relates generally to irrigation equipment, and more particularly to a programmable controller for multiple watering stations.
2. Background Information
Irrigation controllers provide centralized control of watering stations located at remote sites over the field to be irrigated. The controller may include electrical circuitry housed within a stand-alone unit suited for installation at a conveniently accessible outdoor location in or adjacent the field, and it is wired to each of the watering stations where it functions to activate the stations according to a desired watering schedule For large irrigation projects, more than one controller may be utilized, each controlling a share of the watering stations to enable more effective and convenient irrigation, as well as better water conservation.
Some existing controllers accomplish the above under microprocessor control. Once preprogrammed with the start time, duration, and repetition rate desired for each station, the microprocessor produces control signals that are used to activate solenoid valves at the watering stations. This causes water to flow at each station on schedule. The microprocessor does this accurately and dependably, while allowing the user great flexibility in prescribing the exact watering schedule desired.
However, effective irrigation must account for other factors. For example, considerations such as long term weather changes or field condition may dictate changes in the prescribed watering schedule. When this happens, personnel skilled in programming the controller may have to visit each controller location to enter a new watering schedule. Once at the controller location, various pushbuttons and knobs may have to be manipulated to enter the new schedule, and this procedure may be not only inconvenient and time consuming, but also susceptible to error.
Consequently, it is desirable to have a new and improved irrigation controller that alleviates this concern--one that can be more conveniently programmed without the need for skilled personnel to visit and operate each controller.
In addition, short term weather conditions, such as a rainy day, may leave the field in a damp condition so that the scheduled watering is unnecessary. Some existing controllers accept a soil sensor input to account for this condition, and when the sensor indicates that the soil has reached a predetermined level of dampness, the controller is disabled from performing its scheduled watering that day. However, this technique does not permit a partial watering after a light rain. In other words, the soil may be only slightly damp so that a partial watering is still needed. Consequently, it is desirable to have a controller that compensates for varying degrees of soil dampness as well.
Furthermore, watering station malfunctions may occur in the normal course of operations, such as a short circuit or open circuit condition in the lines connecting the controller to the solenoids, or in the solenoids themselves. These may have severe consequences. A short circuit condition, for example, may damage the controller and thereby affect all the watering stations. To overcome this concern, short circuit protection is provided in some existing controllers that results in the controller deactivating the malfunctioning watering station altogether when a short circuit condition occurs.
However, both short circuit and open circuit conditions have other important affects--they alter the watering schedule of the malfunctioning station. An open circuit, for example, may result in a particular watering station remaining inactive so that a portion of the field being irrigated goes without water for an unknown period of time until the malfunction is visually observed. This threatens harm to the field, and so it is desirable to have a controller designed to better manage this problem also.
Other malfunctions may occur. For example, the valve at a particular watering station may fail to open, even though the solenoid is activated properly. When this occurs, increased water pressure may result in damage to various components of the irrigation system. Thus, it is desirable to have a controller designed to overcome this problem as well.